Date of Award

Spring 1-1-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Joseph Ryan

Second Advisor

Gregory Lackey

Third Advisor

Roseanna Neupauer

Abstract

We quantified the occurrences of benzene, toluene, ethylbenzene, and xylenes (BTEX) in water wells in the Denver-Julesburg Basin and determined the extent to which oil and gas is responsible for contamination. Public environmental sampling records were downloaded with computer scripts between 1988 and 2016 from Colorado Oil and Gas Conservation Commission (COGCC) to find water wells where BTEX compounds were above their detection limits. There were 51 BTEX occurrences in water wells, and for each occurrence, we searched oil and gas wells within a half-mile radius for records on surface casing integrity that could indicate fluid or gas leaks into aquifers. From the first BTEX occurrence in 2001 through 2012, there were 1.7 BTEX occurrences per year. After voluntary regulation by the Colorado Oil and Gas Association in 2012, there were 11 BTEX occurrences per year. We found only eight of the 51 water wells were resolved by the COGCC as having an oil and gas well responsible for the contamination. The COGCC stated poor water quality in five of the water wells was unrelated to oil and gas activity but did not acknowledge the presence of BTEX. Nine water wells had documentation for oil and gas well integrity issues or repairs. The remaining 29 water wells had no explanation for the source of BTEX. Five of the BTEX occurrences were above the respective MCL for Colorado drinking water; two of these occurrences above MCLs had no identified source from the COGCC. Thermogenic methane was present in 26% of the BTEX occurrences, which is another indicator of a gas release from an oil and gas well. Biogenic methane was present in 49% of BTEX occurrences; biogenic methane could be from groundwater contact with coalbeds.

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